Martin Heidegger’s Being and Time is regarded as one of the most important philosophical works of the twentieth century. In this work, he engages with ontological questions through an existential analytic of Dasein, largely based upon his interpretation of Aristotle. For Heidegger, Aristotle’s discussion of the soul is unrelated to the modern concept of mind, but rather is an inquiry into being-in-the-world. By exploring Dasein as being-in-the-world, Heidegger eliminates psychological vocabulary from phenomenological research. His philosophy has been received by philosophers such as Gilbert Ryle as a new way of understanding consciousness. It has also influenced the sciences of mind, such as artificial intelligence (AI) research and psychiatry. Heidegger’s idea that the primary mode of being-in-the-world is coping with tools is used to critique the classical information processing model in AI research. The existential concept of mood, Befindlichkeit, is regarded as useful for understanding the experience of mental problems.